Whether they secure that place will depend on whether Moana Pasifika can turn around last week's 7-85 loss to the Chiefs when playing the Hurricanes in Wellington in the following game.
The defending champion Blues have a chance to restore something to their season, especially if they can claim a bonus point win.
The Waratahs could become the third Australian team to make the playoffs if all the stars align, but they have to overcome the Eden Park bogey and see their inexperienced but talented inside-back pairing of halfback Teddy Wilson and first five-eighths Jack Bowen play the games of their lives to give their side a chance.
With so much resting on the result for both sides, Blues coach Vern Cotter said it would be important for the Blues to ensure that if they don't have the ball, they keep the Waratahs out and get the ball back as quickly as possible.
He was aware of the change in the inside backs where halfback Jake Gordon is out with a hamstring injury while Bowen will have his second Super Rugby Pacific start at first five-eighths.
"We've looked at the way they play and what they do with the ball, and how they try to put you under pressure. They're a good team and we're not underestimating them. We need to be at our best."
The choice of Finlay Christie at halfback with Beauden Barrett was deliberate to drive the game to the best effect for the Blues.
Cotter said the Blues would continue the process-driven approach to the contest.
"It is a one-off game, so it's 80 minutes and making sure we perform as best we can. It's been a key focus this week. I've enjoyed having this sort of atmosphere around the play. That's what the boys are in this competition for: knockout games and putting hands on trophies.
"We need to get through this game and put in our best performance if we want to get further.
"There's an edge, enthusiasm, and excitement and there was disappointment with our last outing against Moana Pasifika. We just need to temper that enthusiasm and make sure we're accurate."
The game is also a last chance at home for departing players, hooker Ricky Riccitelli, wing Mark Telea, five-eighths Harry Plummer and flanker Adrian Choate.
Captain and lock Patrick Tuipulotu said the side's disappointing defence of the title it won last year was a motivation to sign for another three years.
"We have a chance, and we've got to believe and make sure we play our last game at home with a bit of pride and get something out of it.
"The result will look after itself if we play well. We want to get something out of it, there is still a chance."